Cherry Audio Revives The Rare Gleeman Pentaphonic

Cherry Audio has turned one of the rarest analog polysynths of the early 1980s into a plug-in. Pentaphonic recreates the Gleeman Pentaphonic, a five-voice instrument built in Mountain View, California by brothers Bob and Al Gleeman in numbers so small that most players have never seen one, let alone played one. It's rarity was attributed by some to the timing of its release, right at the time the DX-7 came out and obliterated many smaller makers. It went out of production in 1983, just a year after it was first released.

Bob Gleeman wanted the sound and flexibility of the emerging programmable polysynths in something smaller and more portable. His brother Al, a computer hardware designer, took the engineering side and came up with five voices of three digitally controlled oscillators each - 15 in total - with analog filtering and amplification, envelopes, chorusing and a 37-note keyboard. A microcomputer handled voice assignment, pitch and sequencer triggers, and the oscillators were stable from power-up rather than drifting while they warmed. A transparent acrylic version, the Pentaphonic Clear, put the circuitry on show. Oscar Peterson was reportedly so taken with one in a San Francisco music store that he played it for two hours, then bought it.

Cherry Audio keeps the original path - three oscillators and noise into a filter, then an amp - and expands around it.

• Oscillators - all eight original waveforms survive: COMP 1, COMP 2, 3%, 12% and 50% pulse, ramp, triangle and sine. Pitch mod, pulse-width modulation and Osc 2 sync are new, as are independent interval tunings on Osc 2 and Osc 3.
• Chorusing - kept as it was on the hardware, detuning oscillators 2 and 3 against oscillator 1 (about +/-0.39% slow, +/-0.78% fast) rather than processing the finished output.
• Filter - switchable 2-pole and 4-pole lowpass with resonance that self-oscillates at maximum, plus keyboard tracking, velocity and modulation.
• Modulation - two LFO-style sections, each with rate, shape, depth, delay, sync, retrig and Action Stick control. Mod 1 offers a rising ramp, Mod 2 a falling saw.
• Envelopes - independent filter and amp ADSRs, with decay and release running to roughly 19.7 seconds, far beyond the original's 5 ms to 5 s.
• Performance - mono, unison and poly modes, up to 16 voices, note priority, glide, unison detune, pitch bend, and a keyboard pressure strip routable to 15 destinations.
• Motion - an arpeggiator plus a 4 x 16-step polyphonic sequencer with pattern chaining, live record and parameter animation of cutoff, resonance, mod and gain.
• Effects - five slots, 22 effects and a dedicated effects modulator LFO with a hardwired target per effect.

The sequencer is the biggest departure from the hardware. The 1982 instrument could record and loop a polyphonic performance while the keyboard stayed playable, even stealing voices back from the sequence. Cherry Audio keeps that performance-oriented idea and adds step programming, four patterns, playback modes, groove controls and parameter animation. Three interface themes, two of them clear-panel designs with adjustable opacity, nod to the different looks the original sported.

It runs standalone or as VST, AU and AAX plug-ins on Windows 7 or newer and macOS 10.13 or newer, needing 196 MB of disk space and an internet connection for activation. Pricing TBC.

More Info: https://cherryaudio.com/products/pentaphonic-synthesizer

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